import React, { useState,useEffect } from "react";



function App() {
 let [opacity, setOpacity] = useState(1)
  useEffect(()=>{
   const id = setInterval(()=>{
      opacity -= 0.1
      if(opacity <= 0){
        opacity = 1
      }
      setOpacity(opacity)
    },100)

    return ()=>{
      clearInterval(id)
    }
  },[])
  return (
    <div>
      <h1 style={{ opacity }}>hello react</h1>
    </div>
  )
}

export default App;
